FIGS. 13A and 13B each show a control unit for a motor such as a motor for driving a robot including an emergency shut-down circuit based on the conventional technology. FIG. 13A shows a power circuit (main circuit power circuit) for driving a motor 1 for driving a robot or the like, and a three-phase power supply unit 2 for the main circuit. The three-phase power supply unit 2 supplies a three-phase AD current via an electromagnetic contactor (MC1) 3 and an amplifier 4 to the motor 1.
FIG. 13B shows a coil energizing circuit for the electromagnetic contactor (MC1) 3. This coil energizing circuit has contacts 5a, 6a, 7a of for a plurality of emergency shut-down switches 5, 6, 7 each based on a push-button system and a switching transistor 9 with the base current controlled by a servo control section 8 connected thereto in series with a coil 3a of the electromagnetic contactor (MC1) 3.
It should be noted that the emergency shut-down switch 5 is an external emergency shut-down switch, which is used by a robot user to stop operations of the robot in an emergency even from a location which is remote from a basic body of the robot or the control unit, and the wiring thereto is short-circuited and returned to a robot control unit, if unnecessary. The emergency shut-down switch 6 is an emergency shut-down switch provided, for instance, on an operation panel, and the emergency shut-down switch 7 is an emergency shut-down switch on a remote control box (teaching box).
When the servo control section 8 flows a base current through the switching transistor 9 in the state where all the emergency shut-down switches 5 to 7 have not been pressed down and all the contacts 5a, 6a, 7a are in the connected state, the switching transistor 9 flows a collector current due to the base current to be turned ON and an exciting current for a coil 3a of the electromagnetic contactor 3 flows between the collector and the emitter. With this operation, the electromagnetic contactor 3 makes the contact operation from the disconnected state to the connected state, and electrical continuity between the three-phase power supply unit 2 and the amplifier 4 is established with the main circuit power voltage loaded to the motor 1 and the motor 1 driven.
In the state as described above where the motor 1 is being driven, if any of the emergency shut-down switches 5 to 7 is pressed, any of the contacts 5a, 6a, 7a corresponding to the pressed switch is set in the disconnected state, and power supply to the coil 3a of the electromagnetic contactor 3 is stopped irrespective of the operating state of the switching transistor 9 with the electromagnetic contactor 3 operated from the disconnected state to the connected state. With this operation, power supply of main circuit power for the motor 1 is disconnected with the motor 1 shut-down.
FIG. 14 shows an emergency shut-down circuit for industrial machines such as robots disclosed in Japanese Patent Laid-Open Publication No. SHO 64-1491. It should be noted that, in FIG. 14, the same reference numerals are assigned to the same components as those shown in FIG. 13 and description thereof is omitted herein.
The emergency shut-down circuit has normally open contacts 11a, 12a, 13a, 14a of electromagnetic relays R11 to R14 provided in power circuits of the motors and only when both the normally open contacts A 15a, 16a of the electromagnetic relays R15, R16 are in the closed state, a DC current is supplied from the control power supply unit 17.
Supplied to coils 15c, 16c of the electromagnetic relays R15, R16 is a DC current via a circuit comprising the emergency shut-down switches 5, 6 and an emergency shut-down circuit formed in a CPU 18 for servo control connected serially to each other, a circuit comprising normally closed contacts 15b, 16b of the electromagnetic contractors R15, R16 and normally closed contacts 11b to 14b of the electromagnetic relays R11 to R14 serially connected to each other, and another normally open contact A (self-sustaining contacts) 15a', 16a' from the control power supply unit 17.
It should be noted that an emergency shut-down release switch 20 for releasing shut-down by the emergency shut-down circuit 19 is connected to the CPU 18.
When set or reset (in the state where all the coils 11c to 16c of the electromagnetic relays R11 to R16 are OFF) for starting, if contacts of the emergency shut-down switches 5, 6 are connected and the emergency shut-down circuit 19 is connected according to an operation of the emergency shut-down release switch 20, a DC current is supplied from the control power supply unit 17 via the emergency shut-down switches 5, 6, emergency shut-down circuit 19, normally closed contacts 15b, 16b of the electromagnetic relays R15, R16, and normally closed contacts 11b to 14b of the electromagnetic relays R11 to R14 to the coils 15c, 16c of the electromagnetic relays R15, R16.
With this operations, both the normally open contacts 15a, 16a of the electromagnetic relays R15, R16 are set in the closed state, a DC current from the control power supply unit 17 is supplied to the coils 11c to 14c of the electromagnetic relays R11 to R14 with the normally open contacts 11a to 14a closed, and a main circuit power current is supplied to the driving circuit 10 of the motor 1. When the coils 11c to 14c of the electromagnetic relays R11 to R14 are excited, the normally closed contacts B 11b to 14b of the electromagnetic relays R11 to R14 are opened, but then as the normally open contacts A 15a', 16a' of the electromagnetic relays R15, R16 for self-sustaining are set in the connected state, power supply to the coils 15c, 16c of the electromagnetic relays R15, R16 is continued, and the normally open contacts 15a, 16a and the normally open contacts 11a to 14a of the electromagnetic relays R11 to R14 are kept in the closed state.
During the operations as described above, if the emergency shut-down switch 5 or 6 is pressed by an operator, or if the emergency shut-down circuit 19 is connected due to self-detection of a failure in the CPU or other components, power supply to the coils 15c, 16c of the electromagnetic relays R15, R16 are stopped with the normally open contacts 15a, 15a', 16a, 16a' opened, and also power supply to the coils 15c, 16c of the electromagnetic relays R15, R16 is stopped with the normally open contacts 11a to 14a disconnected.
With the feature as described above, when an operator shuts down operation of a motor or operation of a motor is shut down as a result of self-detection of a failure, supply of a main circuit power to the motor 1 is disconnected, and operation of the motor 1 is shut down.
FIG. 15 shows an example of a robot control unit incorporating an emergency shut-down circuit and connected to a teaching box based on the conventional technology. A teaching box 30 for controlling a robot in a remote mode is disconnectably connected with a connector 31 to this robot control unit. The normally open contacts 21a, 21b of an electromagnetic relay R21 are connected to motor power circuits 40, 41 respectively.
Power supply to the coil 21c of the electromagnetic relay R2 is controlled by a circuit comprising a robot activating switch 43 based on a momentary switch and an emergency shut-down switch 44 of the control unit connected in series to each other as well as by a circuit comprising normally open contacts 22a, 23a of electromagnetic relays R22, R23 and normally closed contacts B 22a, 23b thereof connected in parallel to each other. It should be noted that an normally open contact 21d of the electromagnetic relay R21 for keeping the activating switch ON is provided in parallel with the robot activating switch 43.
An emergency shut-down switch 32 is provided in the teaching box 30. The emergency shut-down switch 32 is connected with terminals B1 and B2 of the connector 31 to the coil 22c of the electromagnetic relay R22 in the control unit. In the state where the emergency shut-down switch is not being operated, power supply to the coil 22c of the electromagnetic relay R22 is continued, while power supply to the coil 22c of the electromagnetic relay R22 is stopped when the emergency shut-down switch 32 is operated.
Also provided in the control unit is a coil 23c of the electromagnetic relay R23 to which power is supplied through internal short-circuit Bn terminal and Bn-1 terminal of the connector 31 into the control unit, in other words to which power is supplied because it is connected with the connector 31 to the teaching box 30.
Next description is made for operations thereof. When the robot activating switch 43 is pressed, a current is supplied through via an emergency shut-down switch 44 in the connected state and the normally closed contacts 22b, 23b of the electromagnetic relays R22, R23 to the coil 21c of the electromagnetic relay R21, with the normally open contacts 21a, 21b thereof closed and the motor power circuits 40, 41 connected thereto. This state is maintained because the normally closed contact 21d of the electromagnetic relay R21 is closed, even after the robot activating switch 43 is released from the pressed state.
In the operating state as described above, when the emergency shut-down switch 44 in the control unit is pressed, power supply to the coil 21c of the electromagnetic relay R21 is stopped, so that the always-disconnected contacts 21a, 21b, 21c are switched from the closed state to the open state, and power for the motor is disconnected because the motor power circuits 40, 41 are disconnected, thus operation of the motor being shut down.
Also, when the emergency shut-down switch 32 of the teaching box 30 is pressed in the operating state as described above, as power supply to the coil 22c of the electromagnetic relay R22 is stopped, so that the always-disconnected contact 22a is switched from the closed state to the open state with the always-connected contact B 22b switched from the open state to the closed state. In contrast, as the always-disconnected contact 23a of the electromagnetic relay R23 is kept in the closed state and the always-connected contact 23b thereof kept in the open state, power supply to the coil 21c of the electromagnetic relay R21 is stopped with the always-disconnected contacts 21a, 21b, 21c switched from the closed state to the open state, and also power for the motor is disconnected because the motor power circuits 40, 41 are disconnected, thus operation of the motor being stopped.
Also in the operating state as described above, if a jumper line for the connector 31 is removed, as power supply to the coil 23c of the electromagnetic relay R23 is stopped, so that the normally open contact 23a thereof is switched from the closed state to the open state with the normally closed contact 23b switched from the open state to the closed state. In contrast, as the normally open contact A 22a of the electromagnetic relay R22 is kept in the closed state with the normally closed contact 22b kept in the open state, so that power supply to the coil 21c of the electromagnetic relay R21 is stopped with the normally open contacts 21a, 21b, 21c thereof switched from the closed state to the open state, and also the motor power circuits 40, 41 are disconnected, so that power for the motor is disconnected and the motor is shut down.
In the emergency shut-down circuit in any of the examples of conventional technology described above, when contacts of an emergency shut-down switch are short-circuited due to any failure, the emergency shut-down switch does not work effectively even if an operator operates the emergency shut-down switch in an emergency, namely the contacts of the emergency shut-down switch are not disconnected with the motor power not shut down, and the state where a main circuit power voltage is being loaded to the motor is continued, and emergency shut-down is not effected, which is disadvantageous.
Also, there has not been any means enabling an operator to locate, when there occurs any fault, the faulty section.